JP7165724B2 - Polyvinyl alcohol film and method for producing polarizing film using the same - Google Patents

Description

The present invention provides a polyvinyl alcohol film (hereinafter, "polyvinyl alcohol" may be abbreviated as "PVA") having a low haze value, a small number of active agent aggregates, good peelability and film surface quality, and It is related with the manufacturing method of the polarizing film using the same.

PVA films are used in a variety of applications due to their unique properties regarding transparency, optical properties, mechanical strength, water solubility, and the like. In particular, by utilizing its excellent optical properties, PVA film is used as a raw material (original film) for manufacturing polarizing films that constitute polarizing plates, which are the basic components of liquid crystal displays (LCDs). Applications are expanding. A polarizing plate for LCD is required to have high optical performance, and a polarizing film, which is a component thereof, is also required to have high optical performance.

A polarizing plate is generally produced by dyeing a raw PVA film, uniaxially stretching, and, if necessary, fixing treatment using a boron compound or the like to produce a polarizing film, and then applying cellulose triacetate to the surface of the polarizing film. It is produced by laminating a protective film such as a (TAC) film. The raw PVA film is generally produced by a method of drying a film-forming stock solution containing PVA, such as a cast film-forming method.

Many techniques related to PVA films and their manufacturing methods have been known so far. In Patent Document 1, a PVA resin aqueous solution containing polyoxyethylene laurylamine having a polyoxyethylene chain number of 2 as a surfactant is prepared, and the PVA resin aqueous solution is brought into contact with a drum type roll for a contact time of 30 to 120 seconds. It is described that a PVA film having a moisture content of 5% by weight or less was obtained by forming a film by a casting method and adjusting the evaporation rate of water in the PVA aqueous solution to 15 to 30% by weight per minute. According to this document, it is possible to obtain a PVA film having excellent transport performance and no optical defects.

Further, in Patent Document 2, PVA resin, sodium dodecyl sulfate as a sulfate ester salt type anionic surfactant (a), polyoxyethylene dodecyl ether as an ether type nonionic surfactant (b), and a nitrogen-containing nonion PVA films containing lauric acid diethanolamide as system surfactant (c) are described. According to this, it is said that it has excellent optical properties free from optical streaks, optical color unevenness, etc., and can exhibit an excellent effect of anti-blocking property.

Furthermore, in Patent Document 3, PVA resin, polyoxyethylene dodecyl ether as an ether-type nonionic surfactant (a), and polyoxyethylene dodecylamine as two types of nitrogen-containing nonionic surfactants (b) A PVA film containing lauric acid diethanolamide is described. According to this, it has excellent optical properties free from optical streaks, etc., and exhibits excellent blocking resistance. However, in the PVA films obtained in Patent Documents 1 to 3, active agent aggregates are formed, resulting in deterioration of haze, and improvement has been desired.

JP 2011-245872 A Japanese Patent Application Laid-Open No. 2005-206809 Japanese Patent Application Laid-Open No. 2005-206810

The present invention has been made to solve the above problems, and provides a PVA film having a small number of active agent aggregates, a low Haze value, good peelability and film surface quality, and a polarizing film using the same. The object is to provide a manufacturing method.

As a result of extensive studies to achieve the above object, the present inventors have found polyvinyl alcohol (A), an amine-type surfactant (B) represented by the following formula (I) (hereinafter referred to as "amine-type surfactant agent (B)"), and at least one surfactant (C) selected from a sulfate ester salt type or a sulfonate type (hereinafter referred to as "surfactant (C)") ) is contained in a predetermined amount, it is possible to obtain a PVA film with a small number of active agent aggregates, a low Haze value, and good peelability and film surface quality, and completed the present invention. rice field.

［式（Ｉ）中、Ｒは炭素数１０～１６のアルキル基であり、ポリオキシエチレン鎖数（ｍ＋ｎ）が１４～２２である。］
［２］前記界面活性剤（Ｂ）と前記界面活性剤（Ｃ）との重量比率（Ｂ：Ｃ）が１：０．５～１：２０である、［１］に記載のポリビニルアルコールフィルム、
［３］フィルムの幅が１．５ｍ以上である、［１］又は［２］に記載のポリビニルアルコールフィルム、
［４］フィルムの長さが３０００ｍ以上である、［１］～［３］のいずれかに記載のポリビニルアルコールフィルム、
［５］フィルムの厚みが１０～７０μｍである、［１］～［４］のいずれかに記載のポリビニルアルコールフィルム、
［６］［１］～［５］のいずれかに記載のポリビニルアルコールフィルムを染色する工程及び延伸する工程を有する偏光フィルムの製造方法、に関する。That is, the present invention
[1] At least one surfactant (C ), wherein the content of the surfactant (B) is 0.03 to 0.18 parts by weight with respect to 100 parts by mass of the polyvinyl alcohol (A), and the surfactant A polyvinyl alcohol film in which the content of (C) is 0.04 to 0.4 parts by weight with respect to 100 parts by weight of polyvinyl alcohol (A);

[In the formula (I), R is an alkyl group having 10 to 16 carbon atoms, and the number of polyoxyethylene chains (m+n) is 14 to 22. ]
[2] The polyvinyl alcohol film according to [1], wherein the weight ratio (B:C) of the surfactant (B) and the surfactant (C) is 1:0.5 to 1:20.
[3] The polyvinyl alcohol film according to [1] or [2], wherein the width of the film is 1.5 m or more,
[4] The polyvinyl alcohol film according to any one of [1] to [3], which has a length of 3000 m or more,
[5] The polyvinyl alcohol film according to any one of [1] to [4], which has a thickness of 10 to 70 μm.
[6] A method for producing a polarizing film, comprising the steps of dyeing and stretching the polyvinyl alcohol film according to any one of [1] to [5].

The PVA film of the present invention has a small number of active agent aggregates, a low Haze value, and good peelability and film surface quality. Therefore, by using the PVA film as a raw film, a polarizing film having good optical performance can be obtained.

The PVA film of the present invention includes PVA (A), an amine surfactant (B) represented by the following formula (I), and at least one surfactant selected from a sulfate ester salt type or a sulfonate type It consists of a resin composition containing an agent (C).

［式（Ｉ）中、Ｒは炭素数１０～１６のアルキル基であり、ポリオキシエチレン鎖数（ｍ＋ｎ）が１４～２２である。］

[In the formula (I), R is an alkyl group having 10 to 16 carbon atoms, and the number of polyoxyethylene chains (m+n) is 14 to 22. ]

[PVA (A)]
As the PVA (A), one produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester can be used. Examples of vinyl esters include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. One of these may be used alone, or two or more of them may be used in combination, but the former is preferred. Vinyl acetate is preferred as the vinyl ester from the viewpoints of availability, cost, productivity of PVA (A), and the like.

Other monomers copolymerizable with vinyl esters include, for example, ethylene; olefins having 3 to 30 carbon atoms such as propylene, 1-butene and isobutene; acrylic acid or salts thereof; methyl acrylate, ethyl acrylate, acrylic acid Acrylic esters such as n-propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacryl Acids or salts thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate , dodecyl methacrylate, octadecyl methacrylate, and other methacrylic acid esters; salts thereof, acrylamide derivatives such as N-methylolacrylamide or derivatives thereof; methacrylamide derivatives such as methylol methacrylamide or derivatives thereof; N-vinylamides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n- Vinyl ethers such as butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; vinyl cyanides such as acrylonitrile and methacrylonitrile; halogenated compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride vinyl; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters or acid anhydrides; itaconic acid or its salts, esters or acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; can be mentioned. These other monomers may be used singly or in combination of two or more. Among others, ethylene and olefins having 3 to 30 carbon atoms are preferred, and ethylene is more preferred as the other monomer.

The ratio of structural units derived from the other monomers in the vinyl ester polymer is not particularly limited, but is 15 mol% or less based on the number of moles of all structural units constituting the vinyl ester polymer. preferably 5 mol % or less.

Although the degree of polymerization of PVA (A) is not necessarily limited, it is preferably 200 or more, more preferably 300 or more, and even more preferably 400 or more because the film strength tends to decrease as the degree of polymerization decreases. , particularly preferably 500 or more. In addition, if the degree of polymerization is too high, the viscosity of the aqueous solution of PVA (A) or the molten PVA (A) tends to be high, which tends to make film formation difficult. is 9,000 or less, more preferably 8,000 or less, and particularly preferably 7,000 or less. Here, the degree of polymerization of PVA (A) means the average degree of polymerization measured according to the description of JIS K6726-1994, which is measured in water at 30°C after resaponification and purification of PVA (A). It is obtained by the following formula from the intrinsic viscosity [η] (unit: deciliter/g).
Degree of polymerization = ([η] × 10 ⁴ /8.29) ^(1/0.62)

The degree of saponification of PVA (A) is not particularly limited, and for example, PVA (A) of 60 mol% or more can be used. The degree of saponification of (A) is preferably 95 mol% or more, more preferably 98 mol% or more, even more preferably 99 mol% or more. Here, the degree of saponification of PVA (A) is the total number of moles of structural units (typically vinyl ester-based monomer units) that can be converted to vinyl alcohol units by saponification and vinyl alcohol units possessed by PVA (A). means the ratio (mol%) of the number of moles of the vinyl alcohol unit to the The degree of saponification of PVA (A) can be measured according to the description of JIS K6726-1994.

As the PVA (A), one type of PVA may be used alone, or two or more types of PVA having different degrees of polymerization, saponification, and modification may be used in combination. However, the PVA film may be a PVA having an acidic functional group such as a carboxyl group or a sulfonic acid group; a PVA having an acid anhydride group; a PVA having a basic functional group such as an amino group; If PVA having a functional group that promotes is contained, the secondary workability of the PVA film may be lowered due to the cross-linking reaction between PVA molecules. Therefore, in the case where excellent secondary workability is required, such as a raw film for optical film production, PVA (A) having an acidic functional group, PVA having an acid anhydride group, basic The content of PVA having a functional group and the content of neutralized products thereof is preferably 0.1% by mass or less, and more preferably none of them is contained.

The content of PVA (A) in the resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more.

[Amine-type surfactant (B)]
The amine-type surfactant (B) used in the present invention is represented by the following formula (I).

［式（Ｉ）中、Ｒは炭素数１０～１６のアルキル基であり、ポリオキシエチレン鎖数（ｍ＋ｎ）が１４～２２である。］

[In the formula (I), R is an alkyl group having 10 to 16 carbon atoms, and the number of polyoxyethylene chains (m+n) is 14 to 22. ]

In formula (I) above, R is an alkyl group having 10 to 16 carbon atoms. The alkyl group may be linear or branched, but preferably linear. If the number of carbon atoms (alkyl chain length) of R is less than 10, the resulting PVA film will have poor releasability and film surface quality. The carbon number (alkyl chain length) of R is preferably 11 or more, more preferably 12 or more. On the other hand, when the number of carbon atoms (alkyl chain length) of R exceeds 16, the number of active agent aggregates in the resulting PVA film increases, resulting in a high Haze value. The carbon number (alkyl chain length) of R is preferably 15 or less.

In the above formula (I), the polyoxyethylene chain number (m+n) is 14-22. By setting the polyoxyethylene chain number (m+n) within a certain range, formation of activator aggregates is suppressed in the resulting PVA film when used in combination with the surfactant (C) described later. When the polyoxyethylene chain number (m+n) is less than 14, the obtained PVA film has a large number of active agent aggregates and a high Haze value. The polyoxyethylene chain number (m+n) is preferably 15 or more. On the other hand, when the polyoxyethylene chain number (m+n) exceeds 22, the molecular size is large, so the amount of the activator oriented at the interface with the cast drum is reduced, resulting in poor releasability. The polyoxyethylene chain number (m+n) is preferably 21 or less, more preferably 20 or less.

The content of the amine-type surfactant (B) used in the present invention is 0.03 to 0.18 parts by weight per 100 parts by weight of PVA (A). If the content of the amine-type surfactant (B) is less than 0.03 parts by weight, the obtained PVA film will have poor releasability and film surface quality. The content of the amine-type surfactant (B) is preferably 0.04 parts by weight or more, more preferably 0.05 parts by weight or more. On the other hand, when the content of the amine-type surfactant (B) exceeds 0.18 parts by weight, the obtained PVA film has a large number of active agent aggregates and a high Haze value. The content of the amine-type surfactant (B) is preferably 0.16 parts by weight or less, more preferably 0.14 parts by weight or less, and even more preferably 0.12 parts by weight or less. , 0.10 parts by weight or less. The amine surfactant (B) used in the present invention may be used alone or in combination of two or more.

[Surfactant (C)]
The surfactant (C) used in the present invention is at least one selected from sulfate type and sulfonate type. When the surfactant (C) is used alone without the amine-type surfactant (B), the ability to reduce the surface tension is insufficient, and streak-like defects occur in the PVA film. In addition, the present inventors have found that when a surfactant (C) such as a sulfate ester salt type is used alone without using the amine type surfactant (B) together, the acidic substances generated by decomposition are generated in the production equipment. It has been confirmed that corrosion may be caused and, as a result, streak-like defects may occur in the obtained PVA film. In the present invention, the above-described amine-type surfactant (B) and at least one surfactant (C) selected from a sulfate ester salt type or a sulfonate salt type are used in combination at a predetermined content. , Acidic substances generated by decomposition of surfactant (C) such as sulfate ester salt type are neutralized by basic amine type surfactant (B), and it is thought that corrosion of manufacturing equipment can be prevented. be done. As a result, it is possible to obtain a PVA film free from streak-like defects and having excellent film surface quality.

The content of surfactant (C) used in the present invention is 0.04 to 0.4 parts by weight per 100 parts by weight of PVA (A). If the content of the surfactant (C) is outside the above range, the resulting PVA film will have a large number of active agent aggregates, a high haze value, and poor releasability and film surface quality. The content of the surfactant (C) is preferably 0.05 parts by weight or more, more preferably 0.06 parts by weight or more. On the other hand, when the content of the surfactant (C) exceeds 0.4 parts by weight, the resulting PVA film has a large number of droplets, a high haze value, and poor film surface quality. The content of the surfactant (C) is preferably 0.4 parts by weight or less, more preferably 0.3 parts by weight or less, even more preferably 0.2 parts by weight or less. 0.1 part by weight or less is particularly preferred.

In the present invention, the weight ratio (B:C) of the amine type surfactant (B) and the surfactant (C) is preferably 1:0.5 to 1:20. If the weight ratio (B:C) is less than 1:0.5, the Haze value of the resulting PVA film may increase. 8 or more is more preferable. On the other hand, if the weight ratio (B:C) exceeds 1:20, it may cause corrosion of the manufacturing equipment, and as a result, streak-like defects may occur in the resulting PVA film, and it is 1:18 or less. 1:14 or less is more preferable, 1:10 or less is even more preferable, and 1:5 or less is particularly preferable.

Examples of the sulfate salt type include sodium alkyl sulfate, potassium alkyl sulfate, ammonium alkyl sulfate, triethanolamine alkyl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxypropylene alkyl ether sulfate, and sodium polyoxyethylene alkylphenyl ether sulfate. are mentioned. As the alkyl, an alkyl having 8 to 20 carbon atoms is preferable, and lauryl is more preferable. Examples of the sulfonate type include sodium alkylsulfonate, potassium alkylsulfonate, ammonium alkylsulfonate, triethanolamine alkylsulfonate, sodium alkylbenzenesulfonate, disodium dodecyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, and alkylsulfosuccinate. disodium salt, disodium polyoxyethylene alkyl sulfosuccinate, and the like. As the alkyl, an alkyl having 8 to 20 carbon atoms is preferable, and dodecyl is more preferable. These may be used individually by 1 type, and may use 2 or more types together. Among them, the surfactant (C) is preferably of the sulfate ester salt type from the viewpoint of minimizing the number of active agent aggregates in the PVA film to be obtained and further lowering the Haze value.

[PVA film]
From the viewpoint of being able to impart flexibility to the PVA film, the PVA film of the present invention preferably contains a plasticizer. Preferred plasticizers include polyhydric alcohols, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane and the like. These may use only 1 type of plasticizers, and may use 2 or more types of plasticizers together. Among them, ethylene glycol or glycerin is preferable from the viewpoint of compatibility with PVA (A) and availability.

The content of the plasticizer is preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of PVA (A). When the content of the plasticizer is 1 part by mass or more, problems with mechanical properties such as impact strength and process passability during secondary processing are less likely to occur. On the other hand, when the content of the plasticizer is 30 parts by mass or less, the film becomes moderately flexible and the handleability is improved.

The resin composition may further contain components other than PVA, surfactants and plasticizers, if necessary. Such other components include, for example, moisture, antioxidants, ultraviolet absorbers, lubricants, coloring agents, fillers (inorganic particles, starch, etc.), preservatives, antifungal agents, and other components other than those mentioned above. A high molecular compound etc. are mentioned. The content of other components in the resin composition is preferably 10% by mass or less.

The width of the PVA film of the present invention is not particularly limited. It is more preferably 0.5 m or more, particularly preferably 5.0 m or more, and most preferably 5.5 m or more. On the other hand, if the width of the PVA film is too wide, the manufacturing cost of the film forming apparatus for forming the PVA film increases, and furthermore, in the case of producing the optical film with a practical production apparatus, the uniform The width of the PVA film is preferably 7.5 m or less, more preferably 7.0 m or less, and 6.5 m or less. More preferred.

The shape of the PVA film of the present invention is not particularly limited. A shaku film is preferred. The length of the long film (the length in the machine direction) is not particularly limited and can be set as appropriate. The length of the film is preferably 3000m or more. On the other hand, the length of the film is preferably 30000m or less. A long film is preferably wound around a core to form a film roll.

The thickness of the PVA film of the present invention is not particularly limited and can be set as appropriate. The thickness of the film is preferably 10 to 70 μm from the viewpoint of using it as a raw film for producing an optical film such as a polarizing film. In addition, the thickness of the PVA film can be obtained as an average value of values measured at arbitrary 10 points.

The haze and active agent aggregation number of the PVA film of the present invention are measured by the methods described in the examples below. The Haze value is preferably 0.5 or less, more preferably 0.4 or less. In addition, the number of active agent aggregates is preferably 2 or less, more preferably 0.

The method for producing the PVA film of the present invention is not particularly limited. It can be produced by a known method such as a casting film-forming method or a melt-extrusion film-forming method using a film-forming stock solution containing other components. The membrane-forming stock solution may be obtained by dissolving PVA (A) in a liquid medium, or may be obtained by melting PVA (A).

Examples of the liquid medium in the film-forming stock solution include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, Ethylenediamine, diethylenetriamine, and the like can be mentioned, and one or more of these can be used. Among them, water is preferable from the point of view of low load on the environment and recyclability.

The volatile fraction of the membrane-forming stock solution (the content of volatile components such as liquid media removed by volatilization or evaporation during film-forming in the membrane-forming stock solution) varies depending on the film-forming method, film-forming conditions, etc., but is 50 to 50%. It is preferably in the range of 90 mass %, more preferably in the range of 55 to 80 mass %. When the volatile content of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high, and film formation is facilitated. On the other hand, when the volatile content of the membrane-forming stock solution is 90% by mass or less, the thickness uniformity of the obtained PVA film is improved without the viscosity of the membrane-forming stock solution becoming too low.

There is no particular limitation on the specific production method when producing the PVA film of the present invention by a casting film-forming method or a melt extrusion film-forming method using the above-mentioned film-forming stock solution. It can be obtained by casting or discharging a film on a support such as a belt or the like and drying it on the support. If necessary, the obtained film may be further dried with a drying roll or a hot air dryer, heat-treated with a heat treatment device, or humidity-controlled with a humidity control device. The produced PVA film is preferably wound around a core to form a film roll. In addition, both ends in the width direction of the manufactured PVA film may be cut off.

The PVA film of the present invention can be suitably used as a raw film for producing a polarizing film, a retardation film, a special light trapping film, and the like. According to the present invention, a PVA film with high light transmittance and high quality can be obtained. Therefore, it is a preferred embodiment of the present invention that it is an optical PVA film.

A preferred embodiment of the present invention is a method for producing a polarizing film comprising the steps of dyeing and stretching the PVA film. The manufacturing method may further include a fixing treatment step, a drying treatment step, a heat treatment step, and the like. The order of dyeing and stretching is not particularly limited, and the dyeing treatment may be performed before the stretching treatment, the dyeing treatment may be performed simultaneously with the stretching treatment, or the dyeing treatment may be performed after the stretching treatment. . Further, the steps such as stretching and dyeing may be repeated multiple times. In particular, it is preferable to divide the stretching into two or more stages because it facilitates uniform stretching.

Dyes used for dyeing PVA films include iodine or dichroic organic dyes (e.g. DirectBlack 17, 19, 154; DirectBrown 44, 106, 195, 210, 223; DirectRed 2, 23, 28, 31, 37, 39 , 79, 81, 240, 242, 247; DirectBlue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; DirectViolet 9, 12, 51, 98; Dichroic dyes such as DirectYellow 8, 12, 44, 86, 87; DirectOrange 26, 39, 106, 107) can be used. These dyes can be used individually by 1 type or in combination of 2 or more types. Dyeing can usually be carried out by immersing the PVA film in a solution containing the dye, but the treatment conditions and treatment method are not particularly limited.

The method for stretching the PVA film includes a uniaxial stretching method and a biaxial stretching method, the former being preferred. Uniaxial stretching, in which the PVA film is stretched in the machine direction (MD) or the like, may be carried out by either a wet stretching method or a dry heat stretching method. is preferred. The wet stretching method includes stretching a PVA film in pure water, an aqueous solution containing various components such as additives and water-soluble organic solvents, or a water dispersion in which various components are dispersed. Specific examples of the uniaxial stretching method by wet stretching include a method of uniaxial stretching in hot water containing boric acid, a method of uniaxial stretching in a solution containing the dye or a fixing treatment bath described later, and the like. Moreover, the PVA film after absorbing water may be uniaxially stretched in the air, or may be uniaxially stretched by another method.

The stretching temperature in the uniaxial stretching is not particularly limited. A temperature in the range of 50 to 180° C. is preferably employed in the case of hot drawing.

The stretch ratio of the uniaxial stretching treatment (the total stretch ratio when uniaxial stretching is performed in multiple stages) is preferably 4 times or more, and is preferably 4 times or more, from the viewpoint of polarizing performance, until the film is cut as much as possible. is preferred, 5 times or more is more preferred, and 5.5 times or more is even more preferred. The upper limit of the draw ratio is not particularly limited as long as the film is not broken, but it is preferably 8.0 times or less for uniform drawing.

In the production of the polarizing film, it is preferable to carry out a fixing treatment in order to strengthen the adsorption of the dye to the uniaxially stretched PVA film. As the fixing treatment, a method of immersing the PVA film in a general treatment bath containing boric acid and/or a boron compound can be employed. At that time, if necessary, an iodine compound may be added to the treatment bath.

The PVA film that has been uniaxially stretched or uniaxially stretched and fixed is preferably then dried or heat treated. The temperature for the drying treatment or heat treatment is preferably 30 to 150°C, particularly preferably 50 to 140°C. If the temperature is too low, the dimensional stability of the resulting polarizing film tends to deteriorate. On the other hand, if the temperature is too high, the polarizing performance tends to deteriorate due to the decomposition of the dye.

A polarizing plate can be produced by laminating an optically transparent protective film having mechanical strength on one or both sides of the polarizing film obtained as described above. As a protective film in that case, a cellulose triacetate (TAC) film, a cellulose acetate-butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. In addition, PVA-based adhesives, urethane-based adhesives, and the like are generally used as adhesives for bonding the protective film, and among them, PVA-based adhesives are preferably used.

The polarizing plate obtained as described above can be used as a component of a liquid crystal display device by being coated with an acrylic pressure-sensitive adhesive and then pasted onto a glass substrate. When the polarizing plate is attached to the glass substrate, a retardation film, a viewing angle improving film, a brightness improving film, etc. may be attached at the same time.

EXAMPLES The present invention will be specifically described below with reference to Examples, etc., but the present invention is not limited to these Examples.

[Haze]
A 10-m region was cut from the surface layer side of the PVA film roll to be measured, and a square sample of 5 cm in the width direction, 5 cm in the length direction, and 60 μm in thickness was cut out. Thereafter, using a haze meter "HZ-1" manufactured by Suga Test Instruments Co., Ltd., the total light transmittance Tt and diffuse transmittance Td were measured according to ASTM D1003-61, and Haze was calculated from the following formula.
Haze = Td/Tt x 100

[Number of activator aggregates]
A 10-m region was cut from the surface layer side of the PVA film roll to be measured, and a square sample of 1.5 cm in the width direction, 1.5 cm in the length direction, and 60 μm in thickness was cut out. After that, using a differential interference microscope, an image of the central portion in the thickness direction of the film was taken at 1000 magnifications. The photographed image was analyzed using image analysis software “Image-Pro” manufactured by Nippon Roper Co., Ltd., and the number of active agent aggregates in a region of 135 μm×100 μm was measured.

[Peelability]
In the production of a long film of 4000 m or more, when the film was peeled from the cast drum, B was evaluated when it could not be peeled off due to adhesion to the drum, and A was evaluated when it was peeled off without problems.

[Film surface quality]
The cut PVA film was placed between the white screen and the projector in a dark room, and shadows projected on the screen were observed. If discontinuous shading or streak-like shading was observed, it was rated as B, and if the above-mentioned shading was not observed and was uniform, it was rated as A.

Example 1
After immersing 100 parts by mass of PVA chips having a degree of polymerization of 2400 and a degree of saponification of 99.9 mol% in 2500 parts by mass of distilled water at 35°C for 24 hours, centrifugal dehydration is performed to obtain hydrous PVA chips having a volatile content of 70% by mass. Obtained. Per 333 parts by mass of the PVA hydrous chip (100 parts by mass of dry PVA), 10 parts by mass of glycerin, and 0 polyoxyethylene laurylamine having a polyoxyethylene chain number (m + n) of 15 as an amine-type surfactant (B). 0.08 parts by mass and 0.08 parts by mass of sodium polyoxyethylene lauryl ether sulfate as a surfactant (C) were mixed, and the resulting mixture was heated and melted with a vented twin-screw extruder (maximum temperature 130 ° C. ) to obtain a membrane-forming stock solution. After cooling this film-forming stock solution to 100° C. with a heat exchanger, it is extruded from a coat hanger die of 180 cm width onto a drum with a surface temperature of 90° C., dried using a hot air dryer, and then A PVA film having a film thickness of 60 μm and a width of 165 cm was continuously produced by cutting off both ends of the film that had become thicker due to neck-in during film formation. A 4000 m portion of the PVA film was wound around a cylindrical core to form a film roll. Table 1 shows the results of evaluating haze, the number of activator aggregates, peelability and film surface quality of the resulting PVA film by the methods described above.

Examples 2-7, Comparative Examples 1-9
A PVA film was produced and evaluated in the same manner as in Example 1, except that the types and amounts of the amine-type surfactant (B) and surfactant (C) were changed as shown in Table 1. rice field. Table 1 shows the results.

As shown in Table 1, in the PVA films of Examples 1 to 7, the haze was as low as 0.5 or less, the number of activator aggregates was 2 or less, and the peelability and film surface quality were good. On the other hand, in Comparative Examples 1 and 4 using the amine-type surfactant (B) having a polyoxyethylene chain number (m + n) not satisfying 14 to 22, the number of active agent aggregations was large, and the Haze value was not good. . In Comparative Example 2, in which the content of the amine-type surfactant (B) exceeded 0.18 parts by weight, the active agent aggregation number was large and the haze value was not good. In addition, in Comparative Example 3 in which the content of the amine-type surfactant (B) was less than 0.03 parts by weight, the evaluation results of peelability and film surface quality were not good. In Comparative Example 5 using the amine-type surfactant (B) having an alkyl chain length of 18, the activator aggregation number was large and the haze value was not good. In Comparative Example 6, in which the content of the surfactant (C) is less than 0.04 parts by weight, the number of active agent aggregations is large, the Haze value is not good, and the peelability and film surface quality evaluation results are not good. rice field. In addition, in Comparative Example 7 in which the content of the surfactant (C) exceeded 0.4 parts by weight, the number of active agent aggregations was large, the Haze value was not good, and the film surface quality evaluation results were not good. . In Comparative Example 8 in which the surfactant (C) was not used, the number of active agent aggregations was large, the Haze value was not good, and the peelability and film surface quality evaluation results were also not good. In Comparative Example 9 in which the amine surfactant (B) was not used, the evaluation results of the peelability and film surface quality were not good.

Claims (6)

Polyvinyl alcohol (A), an amine-type surfactant (B) represented by the following formula (I), and at least one surfactant (C) selected from a sulfate ester salt type or a sulfonate type surfactant (C) A polyvinyl alcohol film that
The sulfate salt type is sodium alkyl sulfate, potassium alkyl sulfate, ammonium alkyl sulfate, triethanolamine alkyl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxypropylene alkyl ether sulfate, or sodium polyoxyethylene alkylphenyl ether sulfate. can be,
The sulfonate type is sodium alkylsulfonate, potassium alkylsulfonate, ammonium alkylsulfonate, triethanolamine alkylsulfonate, sodium alkylbenzenesulfonate, disodium dodecyldiphenyletherdisulfonate, sodium alkylnaphthalenesulfonate, and alkylsulfosuccinic acid. disodium or disodium polyoxyethylene alkyl sulfosuccinate,
The content of the surfactant (B) is 0.03 to 0.18 parts by weight with respect to 100 parts by mass of the polyvinyl alcohol (A), and the content of the surfactant (C) is the polyvinyl alcohol ( A) 0.04 to 0.4 parts by weight of polyvinyl alcohol film per 100 parts by weight.

[In the formula (I), R is an alkyl group having 10 to 16 carbon atoms, and the number of polyoxyethylene chains (m+n) is 14 to 22. ] 2. The polyvinyl alcohol film according to claim 1, wherein the weight ratio (B:C) of said surfactant (B) and said surfactant (C) is 1:0.5 to 1:20. 3. The polyvinyl alcohol film according to claim 1, wherein the width of the film is 1.5 m or more. The polyvinyl alcohol film according to any one of claims 1 to 3, which has a length of 3000 m or more. The polyvinyl alcohol film according to any one of claims 1 to 4, which has a thickness of 10 to 70 µm. A method for producing a polarizing film, comprising the steps of dyeing and stretching the polyvinyl alcohol film according to any one of claims 1 to 5.